Brush construction



March 3, 1964 R. o. PETERSON 3,122,766

BRUSH CONSTRUCTION Original Filed July 13, 1953 INVENTOR.

RUBEN O. PETERSON ommam mdb,

ATTORNEYS United States Patent M 3,122,765 BRUSH (IQNETRUCTHGN Ruben 0. Feterson, University Heights, fihio, assrgnor to The @sborn Manufacturing fiornpauy, Qleveland, Gino, a corporation of (Bhi Griginal application 51513! 13, 1953, Ser. No. 3'7,421 lupvz Patent No. 3375,1219, dated Feb. 5, 15 6:. lilryraeu and this application .iuly 17, 1962, Ser. No. 219,364 3 Claims. (Ci. 15i79) This invention relates to brush construction, and more particularly to a novel form of high speed rotary brushing tool having operating characteristics never before achieved.

In the manufacture of power driven rotary brushes and the like and particularly wire brushes, it has always een considered necessary to employ brushing material which is as tough as possible and which consequently has relatively high damping capacity and low hardness. Numerous disadvantages always previously considered unavoidable have flowed from such limitations. Wire and the like having a high damping capacity is also relatively soft and the ends of the material accordingly Wear back and round over, thereby losing their cutting ability rather rapidly. Materials of this type do not have the requisite hardness to afiord the degree of cutting action desired for the removal of flash, burrs, oxide coatings and the like. As a result, grindin wheels have generally been employed for this type of work. A grinding operation, however, unless performed with very accurately adjusted equipment, often mars the work surface to a degree requiring a further finishing operation, as by brushing, for example. It is accordingly a primary object of my invention to provide a brushing tool in which the brush material may be of a relatively high degree of hardness and the brush construction designed to provide adequately for the damping of destructive vibration.

Brush material of the type which I employ, e.g. hard tempered steel wire and glass fiber, is not only relatively brittle but its tendency to fracture in use is greatly increased by secondary factors. Very slight scratches on the surface of a glass fiber strand, such as result from interaction of such strands a rapidly rotating brush are sufiicient to cause fracture of the strands and rapid destruction of the brush. While this same effect is an important cause of self-destruction of wire brushes of the type in question, another efiect, namely corrosion due to atmospheric, operating, and storage conditions is a still more serious cause of deterioration. In fact, when opera ing a power brush at a relatively high speed of rotation the impact of the brush wire against the air has the effect of raising the atmospheric pressure thereagainst, greatly increasing the ability of the air to oxidize steel wire, particularly at the somewhat elevated temperatures developed by operation of the brush. Changes in humidity during storage and contact with sweaty fingers are other corrosion accelerators. Once corrosion has commenced, the percentage fracture of the brush material is greatly increased.

Since brushes of this type are commonly employed to apply powdered abrasive and the like to a work-piece, it is obvious that a certain amount of such abrasive will find its way between the strands or bristles and initiate further premature fracture of the same.

When suitable hard brush materials are mounted in a brush back for use as a power brush, there is a tendency for vibrations resulting from operation of the brush to be communicated to concentrated points or areas along the length of the brush material strands. Such concentration of vibratory stresses induces fracture of the brush material at pohits well back from the working face of the 3,1225% Patented Mar. 3, 13%4 brush and greatly reduces the life of the latter. Brush material such as wire has in the past been crimped or twisted to minimize such concentrations of stress. When properly crimped for a given density of a given brush material, the strands support each other to a considerable extent and tend to confine the points of fracture near the working face of the brush. Similarly, when a tuft of brush wire, for example, is twisted to form a coiled knot of such wire, the individual wires thus closely associated tend to support each other and to diffuse the vibratory stresses in such manner as to reduce breakage at points far back from the working face of the brush. Extremely hard brush bristle material, however, usually cannot be crirnped or twisted in a satisfactory manner and even when a degree of crimp may be imparted thereto (as when the material is heated) the tendency toward long fracture in use may nevertheless prove a serious disability.

Certain objects of this invention are therefore as follows:

To provide a brushing tool having improve-d cutting capacity and increased life;

To provide a tool of great cutting capacity yet capable of leaving a relatively smooth finish on the work as compared to the usual grinding wheel or similar fast cutting tool;

To provide a brushing tool modified for more effective application of abrasive;

To provide a brushing tool which will Wear back evenly in use, providing a face of the same width and operating characteristics at all times;

To provide a brushing tool having hard brush material of low damping capacity associated with other material of a high damping capacity effective to prevent concentration of vibratory stresses at points far back from the working face with resultant long fracture of such brush material;

To provide a brushing tool in which the ends of the brush material will themselves progressively crumble or fracture in use and thereby remain sharp and effective rather than rounding over;

To provide a brushing tool in which the brush material is supported in a novel manner elfective both to enhance its cutting capacity and to protect it from scratches, corrosio'n, and similar deteriorating influences.

Other objects of my invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said invention then comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

PEG. 1 is a perspective view substantimly in side elevation of a typical annular rotary brush section;

FIG. 2 is a similar view showing a brushing tool incorporating the brush of FIG. 1;

PEG. 3 is a similar view of another embodiment of my invention incorporating several tiuns of helically coiled brush strip; and

FIG. 4 is a side view of a brushing tool in accordance with my invention generally similar to that of FIG. 2 but formed with a slotted periphery.

Construction Many Well-known types of brushes are adapted to be modified in accordance with my invention to produce my new brushing tool. Reference may be had to my prior Patents Nos. 2,303,386; 2,316,185; and 2,421,647

3 as well as to Whittle Patent No. 2,288,337 and Bickel et al. Patent No. 2,062,047 for typical examples of wellknown power driven rotary brushes which are thus suitable for use.

Referring now more particularly to the drawing, FIG. 1 thereof shows an annular rotary brush section in which stranded brush material 1 extends substantially radially from an inner circular channelform back 2. I have modified brushes of this type by intruding a suitable plastic as described below between the strands of the brush material so that such material is completely embedded in the plastic matrix. Such brush material may be hard low damping capacity steel wire, and the intruded plastic may, for example, be neoprene having a certain amount of a filler such as bentonite incorporated therein together with the usual vulcanizing agents and the like. If desired, other abrasive powders may likewise be incorporated in the plastic material. The plastic is forced into the brush material within a suitable mold, the two sides of which may desirably be faced with cloth annuli 3 so that when, after curing, the finished article is removed from the mold, the cloth will adhere to the sides of the article as shown in FIG. 2. Instead of cloth, similar sheets of nylon or a rubber-containing compound may be employed. These facings serve several purposes. The cloth will prevent the plastic from adhering to the mold, this sometimes being an annoying problem in the molding of rubber and like plastic materials, and especially so in the case of the materials preferred for use in accordance with this invention. The facing of cloth or like material reduces any tendency of the stranded brush material to break out laterally of the highly filled low tensile strength matrix in which it is preferably embedded. The nylon and high tensile rubber-like facings are, of course, also acid and alkali resistant and afford further protection to the tool under certain working conditions. One very satisfactory form of side facing consists of cloth impregnated with a rubber compound, thereby providing both strength and protection from acids and the like. A typical example of a higher tensile strength facing layer material is given below by way of illustration:

Parts Neoprene I100 Zn.0 Mg.O 5 Anti-oxidant 2 Softener 3 Stearic acid 1 Clay 50 The degree of resistance to abrasion of the plastic mamay be controlled by varying the amount of special filler therein, sufiicient filler content causing such plastic to become somewhat crumbly under operating conditions at the working face of the tool.

By properly selecting the brushing material and the plastic matrix, :a tool of this type may be provided in which the plastic wears or crumbles away at a slightly more rapid rate than the hard wire or similar brush material wears back. As a result, the ends 4 of the strands 1 will protrude very slightly from the matrix material and afford a very high cutting capacity while at the same time being resiliently supported in a manner to achieve a long useful life. As the tool wears down in use, the plastic continues to erode and the bristles are progressively exposed so that there is no consequential alteration in the brushing face presented. As compared to the type of grinding wheel generally employed for such work, this new brushing tool, while having a very high cutting capacity which renders it useful for the removal of burrs, flash, and oxide coatings, for example, nevertheless provides a superior finish on the work-piece which usually obviates the necessity of any further finishing operation.

When my preferred hard brush material is employed in a resilient plastic composition as taught herein, any

fracture due to impact or vibration will occur close to the working ends thereof which protrude slightly from the supporting matrix. This serves to keep such ends sharp without reducing the diameter of the tool with undue rapidity. Generally speaking, the less hard of the hard brush materials I may employ may protrude from such supporting matrix to a considerable extent without excessive long fracture in use. When, however, the Knoop hardness of the brush material exceeds 900 it becomes very important that such material protrude only very slightly from such matrix. Similarly, the more resistant to fracture brush material, the more resistant the resilient plastic composition should be to abrasion so that it will crumble away from the working face only sufliciently to expose very short lengths of such brush material. Various compromises may, of course, be effected to obtain a particular desired set of operating characterist-ics.

Instead of employing a single annular brush section as above described, a cylindrical brushing tool having a wider face may be provided by similarly including plastic into several turns of helically wound brush strip 5 as shown in FIG. 3 and molding the same in an appropriate mold.

Chip space may also be provided in the manner illustrated in FIG. 4 of the drawing where a tool generally similar to that of the FIG. 2 embodiment is shown molded with a plurality of radially inwardly extending slots 23 in the outer periphery of the tool. Such slots may conveniently be provided by employing corresponding fins in the molds utilized to mold the plastic body 22. as above described. They may extend diagonally instead of parallel to the tool axis, if desired.

The Brush Material The attitude of workers in the prior art toward the problem of brush material fracture has been to seek tougher materials. While toughness is a desirable quality, it is not as important as several other considerations. Tough steel wire is relatively soft so that the ends of the bristles round over in use and quickly lose their cutting ability. Nor do they have sufiicient resistance to bending and snap action, which is such a desirable characteristic in brushes. Wire of this type has much higher damping capacity with subsequent rapid absorption of vibrations. This self-absorption of vibratory stresses and strains develops internal friction and heat which is a primary cause of fracture. When such absorption of vibratory stresses becomes concentrated at points relatively far removed from the working ends of the strands, long fracture thereof results and the brush consequently has a very short life. By the means herein taught such concentration of stresses at undesired points can be prevented.

A rotary brush revolves at such speeds that each strand is kept vibrating at all times from repeated contact with the work, whether such strands be of the high or low damping capacity type. Low damping capacity material is much less susceptible to self-destruction from this particular cause, however, since it does not do as much work fighting against vibration. Hard brushing materials are therefore desirable not only for their increased cutting capacity but also for the relatively low damping capacity which is generally associated therewith.

In accordance with my invention, I employ brush bristle material having a Knoop hardness in excess of 600, and preferably in excess of 700 or even 800. Strands of materials such as the following are available having the requisite degree of hardness:

'2 nickel Wire (hard drawn, heat treated, relatively pure nickel) The last two materials listed have somewhat greater damping capacity than the others. it is interesting to note that an ordinary brush employing stainless steel wire was observed to have about one-third the life expectancy of a brushing tool employing the same wire but constructed in accordance with my invention. The resilient plastic takes over much of the damping function and literally saves the life of the brush material.

It should be appreciated that most wire, including steel wire, as well as most glass fiber commercially available has a degree of hardness substantially below Knoop 609. The techniques are, however, well known for the production of such wire and glass fiber having a hardness of the order specified.

The Knoop hardness of fine metal Wire filaments, glass fibers and the like may be determined by means of apparatus known as the Knoop indenter which has been developed at the National Bureau of Standards and is now commercially available. The specification for Knoop indenters is set forth in detail in circular letter LC 819 of the National Bureau of Standards, United States Department of Commerce, dated April 1, 1946. T he Knoop indenter is also described in US. Patent No. 2,991,995, and such indenter meeting the specifications or" the National Bureau of Standards is manufactured and sold by Wilson Mechanical Instrument Company, Inc., an associate company of American Chain & Cable Company, lnc., 230 Park Avenue, New York 17, New York.

The relative hardness of different materials may be compared on a Knoop hardness scale in which the Knoop hardness number is expressed by the formula where I=Knoop hardness number L=load (in kilograms) applied to indenter A p unrecovered projected area of indentation (in square l measured length of long diagonal of the indentation Cp=constant relating l to the projecting area in making the Knoop hardness test, it is standard practice to make a number of measurements and to take the average of the results obtained inasmuch as the hardness of some materials tested (cg. steel) is not entirely uniform throughout. When materials such as steel Wire used for brush bristle material are selected of increasing Knoop hardness, they become more and more brittle and susceptible to fracture whereas, as materials of lower Knoop hardness are selected, they become increasingly tough.

The degree of hardness ob. 'nable will, of course, vary with the material employed. Thus glass fiber is available which is considerably harder than most harder grades of steel wire, and the latter may be had harder than stainless steel, for example. It is a general characteristic, however, that as hardness increases so does brittleness and notch sensitivity and the more important becomes the provision of my resilient, high damping capacity material in association therewith. With my modified construction I have employed stranded brush materials having a Knoop hardness in the 800 to 900 range with very great success.

in the case of steel wire, wire having a tensile strength of at least 360,000 p.s.i. attained by tempering (rather than by drawin will ordinarily be in the upper range of Knoop hardness (and scratch hardness) which places it in the category of especially hard materials which I am now enabled to employ with superior results.

The Plastic The plastics employed should ordinarily be able to withstand reasonably high operating temperatures without softening or smearing the work. Examples include:

Rubber (if operating temperatures not too high) Neoprene (polychloroprene) Hycar (modified copolymers of butadiene and acrylonitrile) Nylon (polyamide resins) Vinyl plastics (vinyl polymers and copolymers) Melamine resins (Melamine-formaldehyde reaction prodacts) It will be understood that in employing such plastics the same will ordinarily have included therewith suitable fillers as well as the usual vulcanizing agents or the like to produce the resilient plastic composition for my purpose.

The brush bristles will, of course, reinforce the plastic matrix to some extent and in all cases the plastic material must be strong enough to resist the outward pull of centrifugal force at operating speeds and should not break out in large pieces. It will be sutficicntly resilient to prevent permanent deformation in use and should have a relatively high damping capacity. It is furthermore generally desirable that the plastic material be able to withstand a certain amount of contact (with oil and grease.

When employing wire brush material, plastic compounds such as those having a neoprene base may have their bond to such brush material improved by first applying a cement to the material, such cement preferably comprising a synthetic rubber and resin composition such as is commercially available under the name of Ty-Ply-S (Vanderbilt). The cement may be app-lied by spraying, dipping, or painting the previously thoroughly cleaned brush material. The brush should then be properly dried before intruding the plastic matrix material.

Fillers The plastic which is employed to embed the brush material substantially completely therein should not be so resistant to abrasion and Wear that the ends of the brush bristles will not protrude therefrom. Thus, ordinary tire tread rubber containing certain selected carbon blacks is not suitable for my purpose as it is very resistant to abrasion and will not crumble or Wear back at a rate appreciably greater than that of bristle material embedded therein. A bufilng action is therefore obtained rather than the brushing or cutting action it is an object of my invention to provide. Moreover, it tends to smear the work.

To produce a tool of the type such as that illustrated in the several figures of the drawing and described above, for example, I may first incorporate a selected filler in the plastic material so that such material, while still quite resilient, will be less abrasion resistant and will wear or crumble away in use at a rate slightly faster than the ends of the bristles wear back. The w0rk1n'-g face of the tool will therefore always consist of very short (in some cases on the order of of an inch long) bristles projecting from the resilient plastic matrix. Such construction affords entirely novel characteristics in use, particularly fast cutting action coupled with a relatively smooth finish on the work-piece. It furthermore makes possible the use of brush material otherwise too brittle and makes such use advantageous. As extremely short bits fracture from the ends, such material constantly sharpens itself.

Typical examples of such suitable fillers include:

be employed are commonly combined with several other ingredients, including fillers, in a manner well known in the art. In fact, the final plastic material may comprise a compositionof which only about one-fifth is constituted by the original pure plastic, such as neoprene, for example. The degree of abrasion resistance of such final plastic material relative to that of the brush material may be controlled and modified as necessary by employment of the proper proportion of fillers. When cured, such final plastic material should display at least some degree of resilience and should neither be hard (like hard rubber) nor overly tough and abrasion resistant (like tire tread rubber).

I prefer to employ fillers which are themselves mildly abrasive and therefore afford a cleansing action on the 'work. Such fillers should ordinarily be relatively free from iron oxide and the like and Without tendency to smudge the work so that there will not be deposition of fine corrosion promoting particles thereon. They may also desirably display an ability to absorb certain lubricants which assist in preventing smudging of the work (see below).

Abrasives It is often desired to apply abrasive to a workpiece in addition to the cutting or polishing action which may be produced by the brush material. In fact, brushes are often employed primarily as a means of applying powdered abrasive.

Wire =brush material would be an excellent applicator of such powdered or granular abrasive except for the difficulty in inducing it to hold the same, even when the abrasive is supplied in the form of a paste to assist it in adhering to the Wire strands. By incorporating the abrasive in the plastic employed in the short trim brushing tool above described, such abrasive is continuously supplied to the working face of the tool as the plastic crumbles away. 7

Typical examples of suitable abrasives for use in accordance with my invention include:

Aluminum oxide (Alundum, Aloxite) Silicon carbide (Carborundum, corundurn) Chrome oxide Natural abrasives (e.g. pumice, emery) Mixtures of the above The employment of abrasive in the plastic may further increase the heat generated by the tool in use. Some plastics, when heated sufiiciently, tend to smudge the work but I have found that inclusion of the above-mentioned fillers greatly reduces such tendency, the filler having a lubricating eifect on the freshly cut surface of the Workiece, preventing adherence of the plastic. Small amounts of special lubricants such as paraifin wax, sulphonated oils, and cerotic acid (synthetic beeswax) may also be incorporated in the plastic to enhance such lubricating, smudge-preventing effect. A preferred method of incorporating such lubricant is to treat the filier therewith before adding the latter to the plastic compound. Certain of the clays, such as bentonite, are especially satisfactory for such purpose.

Three specific examples of plastic compositions employed in the production of this type of tool follow.

Parts Hycar 1 100 Filler (whiting) 400 Rubber sub. 50

Softener 3 30 Sulphur 3 Altox 1 Thionex .1

'Zinc oxide 5 Stearic 1 See footnotes at end of table.

t {Bloth Hycar and neoprene are synthetic rubberlike maeria 2 So-called rubber substitutes are commonly employed in compounding rubber and similar plastics, and may comprise blown oils.

3 The softener was a petroleum distillation product. Waxes commonly used in the rubber industry may be employed for this purpose.

It will be noted that a great deal more filler is employed in these examples than in the example of facing composition given above. In fact, the amount of filler may comprise three or four times the amount of filler plastic, and even more.

Annular rotary brush sections having hard, low damping capacity steel wire brush material with a high tensile strength of over 350,000 p.s.i. were placed in molds and the above plastic compositions intruded into such material. After curing, the resultant rotary tools were tested and showed notable effectiveness in such fields as bur removal, flash removal, and removal of oxide coatings from metal surfaces. A finish was left far superior to that obtainable with conventional grinding wheels ap plied by similar offhand methods. It was found that such tools would remove steel burs in approximately five seconds time which required forty-five minutes to remove with the standard brush commercially available best suited for such purpose.

This application is a division of my co-pending application Serial No. 367,421, filed July 13, 3, now Patent 0 No. 3,076,219, which in turn is a continuation-in-part of application Serial No. 50,350, filed September 23, 1948, and now abandoned.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A rotary brushing tool comprising a rigid central member adapted to be mounted for high speed rotation about its axis, resiliently flexible bristle material secured to said member and extending generally radially outwardly therefrom, and a matrix of hi h damping capacity material embedding and joining said bristles in a yielding manner, said tool having a plurality of generally radially extending transverse slots in the outer periphery thereof.

2. A rotary brushing tool of the wheel type having generally radially extending bristles and plastic material yieldingly bonding said bristles together, such wheel having a plurality of generally radially extending narrow transverse slots in the outer periphery thereof between References Cited in the file of this patent groups of said bristles. UNITED STATES PATENTS 3. A rotary brushing tool comprising a generally ciI- 888,129 Tone May 19, 1903 cular body of high damping capaciiy plastic material 1 73 355 M h N ,19,1929 and a quantity of radially extending brush bristles em- 5 1,989,078 Brostrom Jan. 29, 1935 bedded therein, said body having a plurality of generally 2,648,084 Swart Aug. 11, 1953 radially inwardly extending narrow transverse slots in FOREIGN PATENTS the outer peripheral portion thereof 523,879 Great Britain guly 24, 1940 

3. A ROTARY BRUSHING TOOL COMPRISING A GENERALLY CIRCULAR BODY OF HIGH DAMPING CAPACITY PLASTIC MATERIAL A SUCTION UNIT COMPRISING AN IMPELLER, AND AN ELECTRIC MOTOR, ALL POSITIONED WITHIN THE SUCTION SECTION OF THE HOUSING AND SECURED TO AND MOUNTED SURROUNDING SAID OPENING IN THE INTERIOR WALL IN POSITION SO 